1. Field of the Invention
The present invention generally relates to a locking mechanism for a printed circuit assembly (xe2x80x9cPCAxe2x80x9d). More particularly, the invention relates to a self-locking mechanism for a PCA and, more particularly still, to a self-locking mechanism for a hot pluggable PCA that prevents a person from removing the PCA before the system in which the PCA is installed to have a chance to first power down the board.
2. Background of the Invention
Computers and other types of electronic systems typically have one or more circuit boards in addition to a system board. Each circuit includes electronics and performs a desired function. Examples of circuit boards in a computer system include memory cards, sound cards, and graphics cards. Such boards are often referred to as printed circuit assemblies (xe2x80x9cPCAsxe2x80x9d) and that term is used in this disclosure to refer to any type or variation of circuit card usable in an electronic system.
More recently, xe2x80x9chot plugxe2x80x9d PCAs and other devices have been introduced. A hot plug PCA is a circuit card that can be installed in, or removed from, a computer system while the computer system is powered on and operational. Thus, if a PCA fails, that PCA can be removed and a new PCA installed without having to shut down and then reboot the system. Because powering down and rebooting the system is not necessary with hot plug-capable PCAs, maintenance activities can occur much faster with much less of an impact on system operation. This is particularly beneficial in mission critical systems (e.g., banks, Internet Service Providers) that can ill afford to have any down time.
Implementing a hot plug capability in a computer system is not a trivial task and generally requires addressing a number of issues. For instance, the host computer in general may store data or transmit commands to the PCA. It is not desirable to disconnect the PCA from the computer while data is being written to the PCA. Otherwise, the data may be lost. Also, it is not desirable to pull the PCA out of the system, or insert it in the system while live voltages are being provided to the PCA. One way that this issue has been addressed to provide a switch in the system that, when activated, powers down the PCA. Once powered down, the PCA then can be removed. The problem with this approach is that nothing prevents a user from pulling out the PCA before activating the switch. A better solution is needed.
The problems noted above are solved in large part by a self-locking mechanism usable in conjunction with a printed circuit assembly. The self-locking mechanism generally comprises a central actuator, a pair of sliding members on either side of the actuator and one rotating lock member associated with each sliding member. The actuator, sliding members and rotating members preferably are mounted to a top edge of a vertically-mounted circuit board thereby forming the printed circuit assembly.
In accordance with the preferred embodiment of the invention, the printed circuit assembly cannot be removed from the electronic system in which it is mounted unless the self-locking mechanism is unlocked. To unlock the mechanism, the central actuator is turned to an unlocked position. The actuator includes a pair of cam surfaces which, while in the locked position, engage corresponding surfaces of the sliding members thereby preventing the sliding members from being slid. Rotating the actuator to the unlocked position causes an electrical signal to be asserted to the electronic system so that the system can take whatever steps are necessary to disable communications to and power down the electronics on the printed circuit assembly. Once the actuator is turned to the unlocked position, the sliding members then can be slid toward the actuator. The sliding members have non-flat (e.g., curved) tip portions which engage corresponding non-flat surfaces of the rotating lock members. Sliding the sliding members causes the sliding members to push up on the rotating members thereby rotating the rotating members towards an unlocked position. The user can then grab the rotating lock members and pull up to remove the printed circuit assembly from its electronic system. Further, upon installing the PCA into the system, no power is provided to the PCA until the PCA has been fully installed and the actuator turned to the locked position.